1. Field of the Invention
The present invention relates to an improved method and apparatus for cooking starch that is to be used in a commercial laundry application. Even more particularly, the present invention relates to an improved commercial starch cooking method and apparatus wherein a recirculating flow line reticulates the cooking starch solution through a gear pumping arrangement that breaks up lumps in the starch and establishes a circulation of fluid in the vessel to continually mix the starch and clean the vessel wall.
2. General Background of the Invention
During the cooking of starch two phenomena take place. Naturally occurring starch granules undergo considerable physical change, usually "swelling," until they are complete disintegrated, and the starch molecules are hydrolyzed into smaller particles. The resulting modified starch material depends upon processing conditions that are very important in determining the physical characteristics of the final starch solution. The swelling or hydrolyzed modification of starch, if precisely controlled, allows starch to be useful as a size or adhesive.
A compact cooker, reliably and consistently operable by a relatively unsophisticated individual, would be desirable. It is customary in "cooking starch" for laundry purposes to utilize temperatures in the 165 degree Fahrenheit thru 190 degree Fahrenheit range. At higher temperatures, i.e., above 250 Fahrenheit, the chemical and physical make up of the starch will continue to change in that the starch slurries will be unstable. Unstable starch slurries are of little value as size or adhesive.
Several patents have issued for starch cooking devices. Some of the suggested patented systems require the use of a tank float device (e.g., Mitchell 5,437,169) to open and close the water supply valve, via a solenoid. The float is immersed or partially immersed in the aqueous slurry of starch. Immersed operating components in starch solutions are a source of operating trouble. If the float becomes coated with starch, it fails to function, and presents overflow risks.
Some existing starch cookers (e.g., Mitchell 5,437,169; F. H. Martin 2,730,468; and E. W. Miller 1,418,320) use direct steam injection both to cook the starch and to agitate the starch solution. Existing cookers that use steam both to agitate and to cook often create starch solutions having lumps. It is believed that the concentrated heat of the steam directly on the starch solution causes localized heating and a temperature above that which the starch will remain stable. These starch lumps cause uneven starching of the garments and a build up of starch on the press covers when the garments are pressed. Furthermore, direct steam induction results in sediment within the boiler and or steam line to be mixed with the starch solution resulting in contamination and discoloration of the garments.
Some existing starch cookers (e.g., Mitchell 5,437,169, N. E. Elsas 2,940,876; and G. J. Kyame 2,516,884) use a plurality of valves to direct the contents of the containment tank either to the output conduit or the tank circulation. Problems have resulted from starch building up on such valves, including a failure of the valve to function.
Another problem with existing starch cookers is the use of microprocessors to control a plurality of relays and process signals from various controlled communications. Micro processors are particularly susceptible to heat and moisture, and both are abundantly present in commercial laundries. When micro processors are exposed to only minute amounts of moisture and/or heat they often cease to function. It would be desirable to provide an apparatus which did not have aforesaid heat and moisture susceptibility.
Some large laundries use large vats of hot starch solutions and manually transfer hot starch from the vat to the washer. The manual transfer presents a danger of burning the operator. Another problem with this method is the large size of the vats and consequently large quantities of starch. If the entire amount of starch is not used the same day it is prepared, the residual will frequently spoil and impart an unpleasant odor to the garments.
The present invention cooks a quantity of starch solution required by a single wash load of garments, and transfers the single wash quantity automatically as the washer enters the starch event of its cycle.